Exact inequalities for norms of intermediate derivatives of quasiperiodic functions

Mathematical Notes -     

Sharp Kolmogorov-type inequalities for norms of fractional derivatives of multivariate functions

Let C( \mathbbR^m ) C\left( {{\mathbb{R}^m}} \right) be the space of bounded and continuous functions x:\mathbbR^m ? \mathbbR x:{\mathbb{R}^m} \to \mathbb{R} equipped with the norm

Exact constants in inequalities between norms of derivatives of functions

In this article we shall concern ourselves with determining exact (least possible) constants in the inequalities of the form $$\parallel f^{(k)} \parallel _{L_q } \leqslant K\parallel f\parallel _{L_p } ^{\tfrac{{l - k - r - 1 + q - 1}}{{l - r - 1 + p - 1}}} \parallel f^{(l)} \parallel _{L_r } ^{\tfrac{{k - q - 1 + p - 1}}{{l - r - 1 + p^{n - 1} }}} $$ for functions defined on the entire (?∞, ∞), absolutely continuous on any interval together with their (l?1)-th derivatives, and having finite $$l = 2,k = 0,k = 1,q = r = \infty ,1 \leqslant p< \infty $$ is considered.     

Kolmogorov-type inequalities for mixed derivatives of functions of many variables

Let = (₁,...,_d) be a vector with positive components and let D be the corresponding mixed derivative (of order _j with respect to the jth variable). In the case where d > 1 and 0 < k < r are arbitrary, we prove that

Kolmogorov type inequalities for norms of Riesz derivatives of multivariate functions and some applications

Let L _∞,s ¹ (? ^m ) be the space of functions f ∈ L _∞(? ^m ) such that ?f/?x _i ∈ L _s (? ^{m) for each i = 1, ...,m} . New sharp Kolmogorov type inequalities are obtained for the norms of the Riesz derivatives ∥D ^α f∥_∞ of functions f ∈ L _∞,s ¹ (? ^m ). Stechkin’s problem on approximation of unbounded operators D ^α by bounded operators on the class of functions f ∈ L _∞,s ¹ (? ^m ) such that ∥?f∥ _s ≤ 1 and the problem of optimal recovery of the operator D ^α on elements from this class given with error δ are solved.     

Ostrowski type inequalities for functions whose derivatives are s-convex in the second sense

New inequalities of Ostrowski type for functions whose derivatives in absolute value are $s$-convex in the second sense are obtained.     

Some Iyengar-type inequalities on time scales for functions whose second derivatives are bounded

We establish some Iyengar-type inequalities on time scales for functions whose second derivatives are bounded by using Steffensen’s inequality on time scales.     

On inequalities for the norms of intermediate derivatives of multiply monotone functions defined on a finite segment

We study the following modification of the Landau?CKolmogorov problem: Let k; r ?? ?, 1 ?? k ?? r ? 1, and p, q, s ?? [1,??]. Also let MM ^m , m ?? ?; be the class of nonnegative functions defined on the segment [0, 1] whose derivatives of orders 1, 2,??,m are nonnegative almost everywhere on [0, 1]. For every ?? > 0, find the exact value of the quantity $$ \omega_{p,q,s}^{k,r}\left( {\delta; M{M^m}} \right): = \sup \left\{ {{{\left\| {{x^{(k)}}} \right\|}_q}:x \in M{M^m},{{\left\| x \right\|}_p} \leqslant \delta, {{\left\| {{x^{(k)}}} \right\|}_s} \leqslant 1} \right\}. $$ We determine the quantity $ \omega_{p,q,s}^{k,r}\left( {\delta; M{M^m}} \right) $ in the case where s = ?? and m ?? {r, r ? 1, r ? 2}. In addition, we consider certain generalizations of the above-stated modification of the Landau?CKolmogorov problem.     

Merit functions for general mixed quasi-variational inequalities

In this paper, we present some merit functions for general mixed quasi-variational inequalities, and we obtain the equivalent optimization problems to general mixed quasi-variational inequalities. Since the general mixed quasi-variational inequalities include general variational inequalities, quasi-variational inequalities and nonlinear (implicit) complementarity problems as special cases, our results continue to hold for these problems. In this respect, results obtained in this paper represent an extension of previously known results.     

On inequalities for norms of intermediate derivatives on a finite interval

For functionsf which have an absolute continuous (n–1)th derivative on the interval [0, 1], it is proved that, in the case ofn>4, the inequality

On second-order directional derivatives of value functions

Directional derivatives of value functions play an essential role in the sensitivity and stability analysis of parametric optimization problems, in studying bi-level and min–max problems, in quasi-differentiable calculus. Their calculation is studied in numerous works by A.V. Fiacco, V.F. Demyanov and A.M. Rubinov, R.T. Rockafellar, A. Shapiro, J.F. Bonnans, A.D. Ioffe, A. Auslender and R. Cominetti, and many other authors. This article is devoted to the existence of the second order directional derivatives of value functions in parametric problems with non-single-valued solutions. The main idea of the investigation approach is based on the development of the method of the first-order approximations by V.F. Demyanov and A.M. Rubinov.